1. Field of the Invention
This invention relates to an ink, an ink set, an ink cartridge, a recording unit, an image-recording apparatus, a color-image-recording apparatus and an ink-jet recording process.
2. Related Background Art
As black inks for writing implements (such as fountain pens, felt-tip pens and aqueous ball-point pens) and black inks for ink-jet recording, inks making use of carbon black, which is a black colorant providing prints with a high density and also having a superior fastness and so forth have been proposed.
In recent years, detailed research and development have also been made on various aspects of the composition, physical properties and so forth of inks so that good recording can be performed, especially on plain paper such as copy paper, report paper, notebook paper, bond paper and continuous business forms. For example, Japanese Patent Applications Laid-open No. 63-152681 and No. 64-6074 disclose an aqueous pigment ink containing carbon black and a dispersant. Use of such an ink makes it possible to obtain images having a sharp character quality and having a high density.
The present inventors conducted a variety of studies concerning instances where black pigment inks containing, as a black pigment, carbon black containing a dispersant are used in ink-jet recording. As a result, they have found that inks having such constitution can not necessarily provide images with sufficient resistance to rubbing (rub resistance) for some types of recording mediums (e.g., plain paper) and may damage image quality. As a method for improving image rub resistance, the idea of adding a surface-active agent to an ink is proposed to improve the penetration of ink into recording mediums. When, however, the pigment ink is so made up as to be more readily penetrable into recording mediums, there is a problem of damaging character quality characteristics such as image sharpness and high density, which are the inherent advantages of pigment inks.
Accordingly, an object of the present invention is to provide an ink that is a pigment ink having carbon black and a dispersant for carbon black and that can realize high-grade images having superior rub resistance without the loss of such advantages inherent in pigment inks that the sharpness and high density of images formed can be attained, and also to provide an ink set, an ink cartridge, a recording unit, an image-recording apparatus, a color-image-recording apparatus and an ink-jet recording process which make use of such an ink.
Another object of the present invention is to provide an ink that is a pigment ink containing a dispersant-containing carbon black as a black pigment, and is less subject to any influence due to the type of recording medium, can realize a superior image quality, can effectively prevent bleeding when color images are formed and can stably form high-grade images, and also to provide an ink set, an ink cartridge, a recording unit, an image-recording apparatus, a color-image-recording apparatus and an ink-jet recording process that make use of such an ink.
The above objects can be achieved by the invention described below.
One aspect of according to the present invention, there is provided an ink comprising;
at least one salt selected from (M1)2SO4, CH3COO(M1), Phxe2x80x94COO(M1), (M1)NO3, (M1)Cl, (M1)Br, (M1)I, (M1)2SO3 and (M1)2CO3 wherein M1 represents an alkali metal, ammonium or an organic ammonium, and Ph represents a phenyl group;
a carbon black;
a dispersant for the carbon black; and
a medium.
According to another aspect of the present invention, there is provided an ink for ink-jet recording, comprising: a carbon black, a dispersant for the carbon black, and an aqueous medium, and further comprising as a bleeding preventive agent at least one salt selected from (M1)2SO4, CH3COO(M1), Phxe2x80x94COO(M1), (M1)NO3, (M1)Cl, (M1)Br, (M1)I, (M1)2SO3 and (M1)2CO3 wherein M1 represents an alkali metal, ammonium or an organic ammonium, and Ph represents a phenyl group; the ink reducing bleeding of the ink and an aqueous color ink at their boundary area when the ink and the color ink are so applied to a recording medium as to be adjacent to each other, and an ink having the same composition as the above except for not containing the salt causing bleeding when applied to plain paper by ink-jet recording adjacent to an aqueous different-color ink, at their boundary region.
In such an ink, when used as an ink for ink-jet recording, the solid component and liquid component in the ink separates very quickly after they have adhered to a recording medium; hence images can be kept from blurring. This is also very effective for improving image density and image rub resistance and also for keeping the bleeding from occurring. Thus, this ink is preferable as an ink for forming high-quality images by ink-jet recording.
According to a further aspect of the present invention, there is provided an ink set comprising, e.g., a combination of a black ink with an aqueous color ink containing at least one of coloring materials selected from cyan, magenta, yellow, red, green and blue coloring materials; the black ink comprising:
at least one salt selected from (M1)2SO4, CH3COO(M1), Phxe2x80x94COO(M1), (M1)NO3, (M1)Cl, (M1)Br, (M1)I, (M1)2SO3 and (M1)2CO3 wherein M1 represents an alkali metal, ammonium or an organic ammonium, and Ph represents a phenyl group;
a carbon black;
a dispersant for the carbon black; and
a medium.
According to a further aspect of the present invention, there is provided an ink cartridge comprising an ink holder which holds therein an ink comprising:
at least one salt selected from (M1)2SO4, CH3COO(M1), Phxe2x80x94COO(M1), (M1)NO3, (M1)Cl, (M1)Br, (M1)I, (M1)2SO3 and (M1)2CO3 wherein M1 represents an alkali metal, ammonium or an organic ammonium, and Ph represents a phenyl group;
a carbon black;
a dispersant for the carbon black; and
a medium.
According to a further aspect of the present invention, there is provided a recording unit comprising, e.g., an ink holder in which an ink for ink-jet recording is held and a head assembly for ejecting the ink; the ink comprising:
at least one salt selected from (M1)2SO4, CH3COO(M1), Phxe2x80x94COO(M1), (M1)NO3, (M1)Cl, (M1)Br, (M1)I, (M1)2SO3 and (M1)2CO3 wherein M1 represents an alkali metal, ammonium or an organic ammonium, and Ph represents a phenyl group;
a carbon black;
a dispersant for the carbon black; and
a medium.
According to a further aspect of the present invention, there is provided an image-recording apparatus comprising an ink cartridge comprising an ink holder which holds therein an ink for ink jet recording, a recording head for ejecting the ink held in the ink cartridge, and a means for feeding the ink from the ink cartridge, the ink comprising at least one salt selected from (M1)2SO4, CH3COO(M1), Phxe2x80x94COO(M1), (M1)NO3, (M1)Cl, (M1)Br, (M1)I, (M1)2SO3 and (M1)2CO3 wherein M1 represents an alkali metal, ammonium or an organic ammonium, and Ph represents a phenyl group;
a carbon black;
a dispersant for the carbon black; and
a medium.
According to a further aspect of the present invention, there is provided a color-image-recording apparatus comprising the recording unit described above, and a recording unit having an ink holder which holds therein an aqueous color ink containing at least one of a coloring material selected from cyan, magenta, yellow, red, green and blue coloring materials, and a recording head for ejecting the color ink held in the ink holder.
According to a further aspect of the present invention, there is provided a color-image-recording apparatus comprising an ink cartridge comprising an ink holder which holds therein an ink for ink jet recording comprising:
at least one salt selected from (M1)2SO4, CH3COO(M1), Phxe2x80x94COO(M1), (M1)NO3, (M1)Cl, (M1)Br, (M1)I, (M1)2SO3 and (M1)2CO3 wherein M1 represents an alkali metal, ammonium or an organic ammonium, and Ph represents a phenyl group;
a carbon black;
a dispersant for the carbon black; and
a medium, an ink cartridge having an ink holder which holds therein an aqueous color ink containing at least one of coloring materials selected from cyan, magenta, yellow, red, green and blue coloring materials, a recording head for ejecting the respective inks held in the respective ink holders, and means for feeding the respective inks from the respective ink cartridges to the recording head.
According to a further aspect of the present invention, there is provided an ink-jet recording process comprising ejecting an ink for ink-jet recording on the surface of a recording medium and adhering the ink to the recording medium; the ink comprising:
at least one salt selected from (M1)2SO4, CH3COO(M1), Phxe2x80x94COO(M1), (M1)NO3, (M1)Cl, (M1)Br, (M1)I, (M1)2SO3 and (M1)2CO3 wherein M1 represents an alkali metal, ammonium or an organic ammonium, and Ph represents a phenyl group;
a carbon black;
a dispersant for the carbon black; and
a medium.
According to a still further aspect of the present invention, there is provided a process for reducing bleeding of an aqueous black ink and a water-soluble color ink at their boundary region when the aqueous black ink and the water-soluble color ink are so applied to a recording medium as to be in side-by-side contact with each other; the aqueous black ink being an ink comprising:
at least one salt selected from (M1)2SO4, CH3COO(M1), Phxe2x80x94COO(M1), (M1)NO3, (M1)Cl, (M1)Br, (M1)I, (M1)2SO3 and (M1)2CO3 wherein M1 represents an alkali metal, ammonium or an organic ammonium, and Ph represents a phenyl group;
a carbon black; and
a dispersant for the carbon black; which are contained in an aqueous medium.